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The free acid derived from the ester by hydrolysis loses two
molecules of CCX on heating, and gives adipic acid,
= ajc)n.cu,.ciL,.cii,crL,cooH + 2co2.
Cyanacetic ester has similar properties to malonic ester, inas-
much as the mcthylcne hydrogen is replaceable by sodium and
thus by alkyl groups.
Trichloracetic Acid.—This acid may also be obtained by
direct substitution of acetic acid by chlorine (Dumas) (see Prep.
17, p. 87). The oxidation of the corresponding aldehyde is,
however, the more convenient method. Trichloracetic acid
decomposes with alkalis on heating into carbon dioxide and
CC1...COOIT =s CIIC13 H- CO,,.
The reaction resembles the formation of methane from sodium
acetate when heated with soda-lime.
On reduction with sodium or potassium amalgam, trichlor-
acetic acid is converted into acetic acid (Mclscns),
c:ci;,.(.:oon i- 311.5 = cn3.cooi-i + 3110.
Dichloracetic acid may also be obtained from chloral by the
action of potassium cyanide and water,
CCLjCOl! | IL.O -|- RON ^ CIIClo-COOII + KC1 + HCN.
Whereas mono-and tri-chloracetic acid are solid, dichloracetic
acid is a liquid at the ordinary temperature.
Oxalic Acid.—The preparation of oxalic acid by the action
of nitric acid on sugar was introduced by Schcele, and was used
for some lime as a technical process. The vanadium pent-
oxide acts as carrier of oxygen, being alternately reduced to
tetroxide and re-oxidised. The present commercial method is
to heat sawdust with a mixture of caustic potash and soda on
COHEN'S ADV. r. o. c. s